Disclosed herein is an imaging member, such as a flexible photoconductive imaging member, comprised of a photogenerating layer, and overlayed thereon, a charge transport layer comprising multiple regions including a first (bottom) charge transport layer and a second (top) charge transport layer. The second or top charge transport layer contains certain effective amounts of high mobility charge transport components to thereby avoid or minimize undesirable bending stress induced cracking of the charge transport layer of the member, wherein such cracking decreases the lifetime function of the member.
An electrophotographic imaging member device comprising at least one photoconductive insulating layer can imaged by uniformly depositing an electrostatic charge on the imaging surface of the electrophotographic imaging member and then exposing the imaging member to a pattern of activating electromagnetic radiation, such as light, which selectively dissipates the charge in the illuminated areas of the imaging member while leaving behind an electrostatic latent image in the non-illuminated areas. This electrostatic latent image may then be developed to form a visible image by depositing finely divided electroscopic marking toner particles on the imaging member surface. The resulting visible toner image can then be transferred to a suitable receiving member such as paper.
A number of current imaging members are, for example, referred to as multilayered photoreceptors that, in a negative charging system, comprise a supporting substrate, an electrically conductive layer, an optional charge blocking layer, an optional adhesive layer, a charge generating layer, a charge transport layer, and an optional protective or overcoating layer. The imaging members of multilayered photoreceptors can take several forms, for example, flexible belts, rigid drums and the like. Flexible photoreceptor belts may either be seamed or seamless belts. An anti-curl layer may, for example, be employed on the back side of the substrate support, opposite to the electrically active layers, to achieve the desired photoreceptor flatness.
Multilayered photoreceptors, when functioning under electrophotographic machine service conditions, do exhibit typical mechanical failures such as frictional abrasion, wear, and surface cracking. Surface cracking frequently seen in belt photoreceptors is induced either due to dynamic fatigue of the belt flexing over the supporting rollers of a machine belt support module or caused by exposure to airborne chemical contaminants such as solvent vapors and corona species emitted by machine charging subsystems while the photoreceptor belt is subjected to bending stress. The cracks start on the surface of the transport layer, propagate through the transport layer and eventually cause the delamination of the cracked transport layer from the generator layer. The charges on the photoreceptor surface leak through the cracks and cause dark lines printed out on the prints. Such a short photoreceptor life profoundly increases the UMR rate and cost. In fact, photoreceptor surface cracking is one of the common and most urgent mechanical problems seen, particularly in flexible belts. This problem requires quick resolution, because the cracks so generated produce printout defects that seriously impact copy quality.